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                                <h3 id="hashmap&#x7684;&#x7B80;&#x5355;&#x4F7F;&#x7528;">HashMap&#x7684;&#x7B80;&#x5355;&#x4F7F;&#x7528;</h3>
<pre><code class="lang-Java"><span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">TestHashMap</span> </span>{
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title">main</span><span class="hljs-params">(String[] args)</span> </span>{
        Map&lt;String, String&gt; map = <span class="hljs-keyword">new</span> HashMap&lt;&gt;();
        map.put(<span class="hljs-string">&quot;a&quot;</span>,<span class="hljs-string">&quot;aaa&quot;</span>);
        map.put(<span class="hljs-string">&quot;b&quot;</span>,<span class="hljs-string">&quot;bbb&quot;</span>);
        map.put(<span class="hljs-string">&quot;c&quot;</span>,<span class="hljs-string">&quot;ccc&quot;</span>);
        map.put(<span class="hljs-string">&quot;d&quot;</span>,<span class="hljs-string">&quot;ddd&quot;</span>);
        map.put(<span class="hljs-string">&quot;e&quot;</span>,<span class="hljs-string">&quot;eee&quot;</span>);
        System.out.println(map.get(<span class="hljs-string">&quot;a&quot;</span>));
    }
}
<span class="hljs-comment">//&#x8FD0;&#x884C;&#x7ED3;&#x679C;&#xFF1A;aaa</span>
</code></pre>
<p>HashMap&#x5B58;&#x50A8;Key-Value&#xFF08;&#x952E;&#x503C;&#x5BF9;&#xFF09;&#x6570;&#x636E;</p>
<h3 id="hashmap&#x5B9E;&#x73B0;&#x539F;&#x7406;">HashMap&#x5B9E;&#x73B0;&#x539F;&#x7406;</h3>
<p>&#x5728;Java8&#x4E4B;&#x524D;&#xFF0C;&#x901A;&#x8FC7;&#x6570;&#x7EC4;+&#x94FE;&#x8868;&#x5B9E;&#x73B0;</p>
<p>Java8&#x4E2D;&#xFF0C;&#x6539;&#x4E3A;&#x6570;&#x7EC4;+&#x94FE;&#x8868;+&#x7EA2;&#x9ED1;&#x6811;&#x3002;&#x5F53;&#x94FE;&#x8868;&#x957F;&#x5EA6;&#x8D85;&#x8FC7;8&#x65F6;&#xFF0C;&#x5C06;&#x94FE;&#x8868;&#x6539;&#x4E3A;&#x7EA2;&#x9ED1;&#x6811;&#xFF0C;&#x964D;&#x4F4E;&#x6570;&#x636E;&#x67E5;&#x627E;&#x7684;&#x65F6;&#x95F4;&#x590D;&#x6742;&#x5EA6;</p>
<p>HashMap&#x6210;&#x5458;</p>
<p>&#x4E00;&#x4E2A;&#x6570;&#x7EC4;&#xFF0C;&#x6570;&#x7EC4;&#x91CC;&#x9762;&#x6BCF;&#x4E2A;&#x5143;&#x7D20;&#x90FD;&#x662F;&#x94FE;&#x8868;</p>
<p>&#x94FE;&#x8868;&#x5B58;&#x50A8;&#x5BF9;&#x8C61;(Entry)&#xFF1A;&#x5305;&#x62EC;Key&#xFF0C;Value&#xFF0C;next&#xFF0C;hash</p>
<h3 id="hashmap&#x7B80;&#x5355;&#x5B9E;&#x73B0;">HashMap&#x7B80;&#x5355;&#x5B9E;&#x73B0;</h3>
<p>&#x5B9A;&#x4E49;Map&#x63A5;&#x53E3;</p>
<pre><code class="lang-Java"><span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">interface</span> <span class="hljs-title">MyMap</span>&lt;<span class="hljs-title">K</span>,<span class="hljs-title">V</span>&gt; </span>{

    <span class="hljs-function"><span class="hljs-keyword">public</span> V <span class="hljs-title">put</span><span class="hljs-params">(K k,V v)</span></span>;
    <span class="hljs-function"><span class="hljs-keyword">public</span> V <span class="hljs-title">get</span><span class="hljs-params">(K k)</span></span>;
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">int</span> <span class="hljs-title">size</span><span class="hljs-params">()</span></span>;
    <span class="hljs-class"><span class="hljs-keyword">interface</span> <span class="hljs-title">Entry</span>&lt;<span class="hljs-title">K</span>,<span class="hljs-title">V</span>&gt;</span>{
        <span class="hljs-function"><span class="hljs-keyword">public</span> K <span class="hljs-title">getKey</span><span class="hljs-params">()</span></span>;
        <span class="hljs-function"><span class="hljs-keyword">public</span> V <span class="hljs-title">getValue</span><span class="hljs-params">()</span></span>;
    }

}
</code></pre>
<p>HashMap&#x7B80;&#x5355;&#x5B9E;&#x73B0;</p>
<pre><code class="lang-Java"><span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">MyHashMap</span>&lt;<span class="hljs-title">K</span>, <span class="hljs-title">V</span>&gt; <span class="hljs-keyword">implements</span> <span class="hljs-title">MyMap</span>&lt;<span class="hljs-title">K</span>, <span class="hljs-title">V</span>&gt; </span>{

    <span class="hljs-comment">//&#x6570;&#x7EC4;&#x52A0;&#x94FE;&#x8868;</span>
    <span class="hljs-keyword">private</span> Entry&lt;K, V&gt;[] table;
    <span class="hljs-keyword">private</span> <span class="hljs-keyword">int</span> size = <span class="hljs-number">0</span>;
    <span class="hljs-keyword">private</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">int</span> defaultLength = <span class="hljs-number">16</span>;

    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-title">MyHashMap</span><span class="hljs-params">()</span> </span>{
        table = <span class="hljs-keyword">new</span> Entry[defaultLength];
    }

    <span class="hljs-meta">@Override</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> V <span class="hljs-title">put</span><span class="hljs-params">(K k, V v)</span> </span>{
        <span class="hljs-comment">//1.key&#x8FDB;&#x884C;hash  2.&#x5BF9;&#x5E94;&#x6570;&#x7EC4;&#x4E0B;&#x6807;  3.&#x5982;&#x679C;&#x662F;null  4.&#x662F;&#x5426;&#x53EF;&#x4EE5;&#x5B58;&#x50A8;</span>
        <span class="hljs-keyword">int</span> index = hash(k);
        Entry&lt;K, V&gt; entry = table[index];
        <span class="hljs-keyword">if</span> (<span class="hljs-keyword">null</span> == entry) {
            table[index] = <span class="hljs-keyword">new</span> Entry&lt;&gt;(k, v, <span class="hljs-keyword">null</span>, index);
        } <span class="hljs-keyword">else</span> {
            table[index] = <span class="hljs-keyword">new</span> Entry&lt;&gt;(k, v, entry, index);
        }
        size++;

        <span class="hljs-keyword">return</span> table[index].getValue();
    }

    <span class="hljs-function"><span class="hljs-keyword">private</span> <span class="hljs-keyword">int</span> <span class="hljs-title">hash</span><span class="hljs-params">(K k)</span> </span>{
        <span class="hljs-keyword">int</span> index = k.hashCode() % (defaultLength - <span class="hljs-number">1</span>);
        <span class="hljs-keyword">return</span> Math.abs(index);
    }

    <span class="hljs-meta">@Override</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> V <span class="hljs-title">get</span><span class="hljs-params">(K k)</span> </span>{

        <span class="hljs-keyword">if</span> (size == <span class="hljs-number">0</span>) {
            <span class="hljs-keyword">return</span> <span class="hljs-keyword">null</span>;
        }
        <span class="hljs-comment">//hash&#x51FA;&#x6765;&#x7684;index  &#x83B7;&#x53D6;&#x5230;&#x5F53;&#x524D;Entry&#x5BF9;&#x8C61;  &#x5224;&#x65AD;&#x5BF9;&#x8C61;&#x6709;&#x6CA1;&#x6709;&#x503C;  &#x6BD4;&#x8F83; &#x5728;&#x7EE7;&#x7EED;&#x67E5;&#x627E;&#x76F4;&#x5230;  key  hashcode</span>
        <span class="hljs-keyword">int</span> index = hash(k);

        Entry&lt;K, V&gt; entry = getEntry(k, index);

        <span class="hljs-keyword">return</span> entry == <span class="hljs-keyword">null</span> ? <span class="hljs-keyword">null</span> : entry.getValue();
    }

    <span class="hljs-function"><span class="hljs-keyword">private</span> Entry&lt;K, V&gt; <span class="hljs-title">getEntry</span><span class="hljs-params">(K k, <span class="hljs-keyword">int</span> index)</span> </span>{
        <span class="hljs-keyword">for</span> (Entry&lt;K, V&gt; entry = table[index]; entry != <span class="hljs-keyword">null</span>; entry = entry.next) {
            <span class="hljs-keyword">if</span> (entry.hash == index &amp;&amp; (k == entry.getKey() || k.equals(entry.getKey()))) {
                <span class="hljs-keyword">return</span> entry;
            }
        }
        <span class="hljs-keyword">return</span> <span class="hljs-keyword">null</span>;
    }

    <span class="hljs-meta">@Override</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">int</span> <span class="hljs-title">size</span><span class="hljs-params">()</span> </span>{
        <span class="hljs-keyword">return</span> size;
    }

    <span class="hljs-keyword">static</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">Entry</span>&lt;<span class="hljs-title">K</span>, <span class="hljs-title">V</span>&gt; <span class="hljs-keyword">implements</span>  <span class="hljs-title">MyMap</span>.<span class="hljs-title">Entry</span>&lt;<span class="hljs-title">K</span>, <span class="hljs-title">V</span>&gt; </span>{

        K k;
        V v;
        MyHashMap.Entry&lt;K, V&gt; next;
        <span class="hljs-keyword">int</span> hash;

        <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-title">Entry</span><span class="hljs-params">(K k, V v, MyHashMap.Entry&lt;K, V&gt; next, <span class="hljs-keyword">int</span> hash)</span> </span>{
            <span class="hljs-keyword">this</span>.k = k;
            <span class="hljs-keyword">this</span>.v = v;
            <span class="hljs-keyword">this</span>.next = next;
            <span class="hljs-keyword">this</span>.hash = hash;
        }


        <span class="hljs-meta">@Override</span>
        <span class="hljs-function"><span class="hljs-keyword">public</span> K <span class="hljs-title">getKey</span><span class="hljs-params">()</span> </span>{
            <span class="hljs-keyword">return</span> k;
        }

        <span class="hljs-function"><span class="hljs-keyword">public</span> V <span class="hljs-title">getValue</span><span class="hljs-params">()</span> </span>{
            <span class="hljs-keyword">return</span> v;
        }
    }
}
</code></pre>
<p>&#x6D4B;&#x8BD5;</p>
<pre><code class="lang-Java"><span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">TestMyHashMap</span> </span>{
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title">main</span><span class="hljs-params">(String[] args)</span> </span>{
        MyMap&lt;String, String&gt; map = <span class="hljs-keyword">new</span> MyHashMap();
        map.put(<span class="hljs-string">&quot;yll&quot;</span>, <span class="hljs-string">&quot;yll&quot;</span>);
        System.out.println(map.get(<span class="hljs-string">&quot;yll&quot;</span>));
        System.out.println(map.size());
    }
}
<span class="hljs-comment">/*&#x8FD0;&#x884C;&#x7ED3;&#x679C;&#xFF1A;
yll
1
*/</span>
</code></pre>
<p>&#x8FD9;&#x91CC;&#x53EA;&#x5B9E;&#x73B0;&#x4E86;Java8&#x4E4B;&#x524D;&#x7684;&#x6570;&#x7EC4;&#x52A0;&#x94FE;&#x8868;&#x5F62;&#x5F0F;</p>
<h3 id="hashmap&#x6CE8;&#x610F;&#x4E8B;&#x9879;">HashMap&#x6CE8;&#x610F;&#x4E8B;&#x9879;</h3>
<p>HashMap&#x662F;&#x7EBF;&#x7A0B;&#x4E0D;&#x5B89;&#x5168;&#x7684;&#xFF0C;put&#x65B9;&#x6CD5;&#x548C;&#x6269;&#x5BB9;&#x65F6;&#x90FD;&#x662F;&#x4E0D;&#x5B89;&#x5168;&#x7684;</p>
<p>&#x4F46;&#x662F;get&#x65B9;&#x6CD5;&#x662F;&#x7EBF;&#x7A0B;&#x5B89;&#x5168;&#x7684;</p>
<h3 id="hash&#x7684;&#x4F5C;&#x7528;">hash&#x7684;&#x4F5C;&#x7528;</h3>
<p>hashcode&#x901A;&#x8FC7;hash&#x51FD;&#x6570;&#x8BA1;&#x7B97;&#x5F97;&#x5230;&#xFF0C;hashcode&#x5C31;&#x662F;&#x5728;hash&#x8868;&#x4E2D;&#x5BF9;&#x5E94;&#x7684;&#x4F4D;&#x7F6E;</p>
<p>&#x6BCF;&#x4E2A;&#x5BF9;&#x8C61;&#x90FD;&#x6709;hashcode&#xFF0C;&#x5C06;&#x5BF9;&#x8C61;&#x7684;&#x7269;&#x7406;&#x5730;&#x5740;&#x8F6C;&#x6362;&#x4E3A;&#x4E00;&#x4E2A;&#x6574;&#x6570;&#xFF0C;&#x5C06;&#x6574;&#x6570;&#x901A;&#x8FC7;hash&#x8BA1;&#x7B97;&#x5F97;&#x5230;hashcode</p>
<p>hashCode&#x65B9;&#x6CD5;&#x7684;&#x5B58;&#x5728;&#x662F;&#x4E3A;&#x4E86;&#x51CF;&#x5C11;equals&#x65B9;&#x6CD5;&#x7684;&#x8C03;&#x7528;&#x6B21;&#x6570;&#xFF0C;&#x4ECE;&#x800C;&#x63D0;&#x9AD8;&#x7A0B;&#x5E8F;&#x6548;&#x7387;</p>
<h4 id="hashcode&#x4E0E;equals">hashCode()&#x4E0E;equals()</h4>
<p>Java&#x7684;&#x57FA;&#x7C7B;Object&#x4E2D;&#x7684; equals()&#x65B9;&#x6CD5;&#x7528;&#x4E8E;&#x5224;&#x65AD;&#x4E24;&#x4E2A;&#x5BF9;&#x8C61;&#x662F;&#x5426;&#x76F8;&#x7B49;&#xFF0C;hashCode()&#x65B9;&#x6CD5;&#x7528;&#x4E8E;&#x8BA1;&#x7B97;&#x5BF9;&#x8C61;&#x7684;&#x54C8;&#x5E0C;&#x7801;&#x3002;equals()&#x548C;hashCode()&#x90FD;&#x4E0D;&#x662F;final&#x65B9;&#x6CD5;&#xFF0C;&#x90FD;&#x53EF;&#x4EE5;&#x88AB;&#x91CD;&#x5199;(overwrite)</p>
<h4 id="hashcode&#x65B9;&#x6CD5;">hashCode&#x65B9;&#x6CD5;</h4>
<p>hashCode()&#x662F;&#x4E00;&#x4E2A;native&#x65B9;&#x6CD5;&#xFF08;&#x4E00;&#x4E2A;Native Method&#x5C31;&#x662F;&#x4E00;&#x4E2A;java&#x8C03;&#x7528;&#x975E;java&#x4EE3;&#x7801;&#x7684;&#x63A5;&#x53E3;&#xFF09;&#xFF0C;&#x800C;&#x4E14;&#x8FD4;&#x56DE;&#x503C;&#x7C7B;&#x578B;&#x662F;&#x6574;&#x5F62;</p>
<h3 id="hashmap&#x4E2D;&#x7684;hash&#x51FD;&#x6570;">HashMap&#x4E2D;&#x7684;hash&#x51FD;&#x6570;</h3>
<pre><code class="lang-Java"><span class="hljs-function"><span class="hljs-keyword">static</span> <span class="hljs-keyword">final</span> <span class="hljs-keyword">int</span> <span class="hljs-title">hash</span><span class="hljs-params">(Object key)</span> </span>{
    <span class="hljs-keyword">int</span> h;
    <span class="hljs-keyword">return</span> (key == <span class="hljs-keyword">null</span>) ? <span class="hljs-number">0</span> : (h = key.hashCode()) ^ (h &gt;&gt;&gt; <span class="hljs-number">16</span>);
}
</code></pre>
<p>&#x8FD9;&#x6BB5;&#x4EE3;&#x7801;&#x7C7B;&#x4F3C;&#x4F5C;&#x7528;&#x662F;&#x4E3A;&#x4E86;&#x589E;&#x52A0;hashcode&#x7684;&#x968F;&#x673A;&#x6027;</p>

                                
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